Drill bits use rotary energy provided by a drill string to cut through downhole formations and advance the tool string further into the earth Often, the drill string is directed along complex drilling trajectories to maximize drilling resources and save drilling costs.
U.S. Pat. No. 5,803,185 to Barr et at which is herein incorporated by reference for all that it contains, discloses a steerable rotary drilling system with a bottom hole assembly which includes, in addition to the drill bit, a modulated bias unit and a control unit, the bias unit comprising a number of hydraulic actuators around the periphery of the unit, each having a movable thrust member which is hydraulically displaceable outwardly for engagement with the formation of the borehole being drilled. Each actuator may be connected, through a control valve, to a source of drilling fluid under pressure and the operation of the valve is controlled by the control unit so as to modulate the fluid pressure supplied to the actuators as the bias unit rotates. If the control valve is operated in synchronism with rotation of the bias unit the thrust members impart a lateral bias to the bias unit, and hence to the drill bit, to control the direction of drilling.
U.S. Pat. No. 6,150,822 to Hong, et al., which is herein incorporated by reference for all that it contains, discloses a microwave frequency range sensor (antenna or wave guide) disposed in the face of a diamond or PDC drill bit configured to minimize invasion of drilling fluid into the formation ahead of the bit. The sensor is connected to an instrument disposed in a sub interposed in the drill stem for generating and measuring the alteration of microwave energy.
U.S. Pat. No. 6,814,162 to Moran, et al., which is herein incorporated by reference for all that it contains, discloses a drill bit, comprising a bit body, a sensor disposed in the bit body, a single journal removably mounted to the bit body, and a roller cone rotatably mounted to the single journal. The drill bit may also comprise a short-hop telemetry transmission device adapted to transmit data from the sensor to a measurement-while-drilling device located above the drill bit on the drill string.
U.S. Pat. No. 5,415,030 to Jogi, et al., which is herein incorporated by reference for all that it contains, discloses a method for evaluating formations and bit conditions. The invention processes signals indicative of downhole weight on bit (WOB), downhole torque (TOR), rate of penetration (ROP), and bit rotations (RPM), while taking into account bit geometry to provide a plurality of well logs and to optimize the drilling process.
U.S. Pat. No. 5,363,926 to Mizuno, which is herein incorporated by reference for all that it contains, discloses a device for detecting inclination of a boring head of a boring tool.
The prior art also discloses devices adapted to steer the direction of penetration of a drill string. U.S. Pat. No. 6,913,095 to Krueger, U.S. Pat. No. 6,092,610 to Kosmala, et al., U.S. Pat. No. 6,581,699 to Chen, et al., U.S. Pat. No. 2,498,192 to Wright, U.S. Pat. No. 6,749,031 to Klemm, U.S. Pat. No. 7,013,994 to Eddison, which are all herein incorporated by reference for all that they contain, discloses directional drilling systems.